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FreeBSD-EN-21:04.zfs                                            Errata Notice
                                                          The FreeBSD Project

Topic:          zfs recv fails to propagate snapshot deletion

Category:       core
Module:         zfs
Announced:      2021-01-29
Affects:        FreeBSD 12.2
Corrected:      2020-12-01 08:15:18 UTC (stable/12, 12.2-STABLE)
                2021-01-29 01:20:55 UTC (releng/12.2, 12.2-RELEASE-p3)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

The zfs send/receive commands are used to efficiently copy datasets from one
location to another.  With the -i or -I flags, zfs send can incrementally
update an already-copied dataset.  When using the -R flag with zfs send and the
- -F flag with zfs receive, zfs receive will delete any snapshots on the
destination that have already been deleted on the source.

II.  Problem Description

A regression in FreeBSD 12.2 causes zfs receive to fail to delete snapshots
that have been deleted on the source side.

III. Impact

Backup and replication systems based on ZFS send/receive that manage snapshots
solely on the source side will fail to delete snapshots on the destination
side.  This may lead to out-of-space conditions on the destination.

IV.  Workaround

Errant snapshots can be manually removed from the destination with "zfs destroy".

Backup and replication systems that don't use the -R flag with zfs send will be
unaffected.  For example, sysutils/zrepl is unaffected.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-21:04/zfs.patch
# fetch https://security.FreeBSD.org/patches/EN-21:04/zfs.patch.asc
# gpg --verify zfs.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart all daemons that link directly to libzfs.so.  A restart is not required
for daemons that invoke the zfs executable.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r368233
releng/12.2/                                                      r369173
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=249438>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-21:04.zfs.asc>
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